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*Show notes - Metal Detector Build
Surf Pi construction notes and helpful links
1. You can buy the kit from here
Please note that the kit is essentially the ciruit board and electrical components (including switches and piezo). The coil, coil housing, circuit housing and metal detector pole you will have to build yourself. The seller clearly marks
the components which is great.
2. Build instructions, circuit diagram, photos and other useful information are here
Pay special attention to the way the electrolytics are put on the board. They don't all go the same way - a trap for the unwary.
3. Make sure that things like the pole going to the coil attachment are non conductive as metal will interfere with the operation of the metal detector. PVC is good.
4. Before building, wire in a 12v, 400 ma fuse into one of the power lines. Better to burn that out than any electrical components.
5. You will need to supply the detector with 12v. 8x 1.5v batteries will do but you will need to get the battery holder and batteries separately.
6. I made my pinpointer by using a dual pole switch to switch the two wires going to my coil to instead go to my handmade pinpointer. The pinpointer, stuffed inside some pvc with caps on the end was 50 turns of 0.81mm enamel coated
copper wire wrapped around a ferrite rod with a little carboard insulatng the ferrite rod from the wire turns.That detected metal up to 3“.
7.Its recommended to use coax for the wire going to your coil but I found speake wire worked ok.
8. My coil was 8.5” diameter being 22 rings of 0.81mm enamel coated copper wire.
You can make this by getting a board and making a ring of nails the right size then just wrap your wire around that. YOu can then tape the wire to keep it as one big ring and just remove the nails.
There is also mention of wrapping the coil in aluminium foil and leaving a small gap between the two wires going to the coil but I didn't find this necessary to do. You can also use speaker wire to make a spiral coil. There is a lot of
discussion on the forums about making coils for this build. Experimenting is half the fun! The Surf Pi is pretty tolerant of a wide range of coil sizes and shapes.
9. If you run into problems you can get support and help at the Geotech forums
http://www.geotech1.com/forums/forum.php
10. Expect to get depth of up to 30cm (12“) depending on the size and type of metal.
11. Safety first! Unfortanately there can be buried needles on beaches so use gloves, and better still use a plastic hand sieve to sift the sand.
Also wear lots of sunscreen.